Philadelphia

West Chester KOA also has very nice canoeing right along the Brandywine River with direct access from campground. Very nice owners and overall a great place.

KOA West Chester is the campground most use for Philly. Check out the public transportation before you decide. There are campgrounds in PA north of Philly - one in Quakertown, but no public transportation.

The West Chester KOA has a guided tour shuttle from the campground to Philadelphia that includes Valley Forge.

http://koa.com/campgrounds/philadelphia/

You might check out Timberlane in Clarksboro, NJ (http://timberlanecampground.com/). I've never stayed there and don't know about public transit, but it's pretty close to Philly.

Think the one mentioned might be your only choice. Very few CGs at all near Philly, let alone one close to mass transit.

You can stay in the KOA at West Chester and take the train into Philly.